Field of the Invention
The invention relates generally to probes for spectroscopic measuring devices and, more particularly, to a transverse optical transmission probe.
Description of the Related Art
A variety of sampling devices are currently available for use in optical spectroscopy (primarily near-infrared and UV-visible). These generally use optical fibers to couple to an appropriate instrument. They fall into the following categories and suffer from the noted problems:                1 Single pass transmission probes. An example is the Axiom Analytical FPT-850. These probes provide high performance but involve numerous manufacturing steps and hence do not meet the low cost requirement of our invention.        2. Double pass transflectance probes. These probes are somewhat less expensive to produce than the single pass probes but have significant performance limitations. In particular, the sample gap needs to be one half of the desired pathlength thereby restricting sample flow.        3. Transmission cells. Commercial transmission cells are generally too costly for our current requirements. One could envision a less expensive cell. But it would be difficult to provide the serviceability required for the envisioned application with a transmission cell form factor.        
There remains a need, therefore, for a transverse optical transmission probe that is compatible with water based samples, is capable of being produced at very low cost in substantial volume, has a relatively small sample gap but not so small that it causes sample retention in the sample gap and restricts sample flow; and is suitable for easy service and replacement in the field.